The most professional devices that can measure an engine's
power and torque are the engine dynamometers. They are used by the engine
manufacturers themselves.
In order to perform the measurements on the engine (this is
done before the engine in mounted into the chassis), the engine is connected to
the dynamometer with a shaft. Afterwards, the engine is ignited, and it is set
to run at a constant speed, and the torque that is applied to the dynamometer
is exactly the engine's torque. The results of these measurements are quite
accurate and there are no losses because of friction.
The new-generation dynamometers are connected to computers
and they are very easy to handle and operate. They can almost perfectly
simulate racing and normal driving conditions.
When driving on the road, there are a few factors that may
modify the way an engine acts and the power it produces. Among these there's
the air's temperature, level of humidity and also its pressure. These can be
taken into consideration when testing an engine with a dynamometer, with the
help of some formulas the power that an engine can give can be calculated under
several types of meteorological conditions, so how the power modifies when the
air pressure drops for example can be easily calculated.
Real-life conditions can be simulated by increasing the
temperature at which the dynamometer tests are performed, because the engine is
heating up as it runs.
Anyway, it mustn't be forgotten that once the engine is
installed into the chassis it will connect to the drivetrain, and this plus a
few more things will make an important part of the power to be absorbed, so the
readings from an engine dynamometer will be a little different. To measure the
power of the dynamometer 'at the wheels' a chassis dynamometer is required.
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